Amazona diadema was formerly considered to be an isolated subspecies of the red-lored amazon (Amazona autumnalis),[2] a widespread species in Mexico, Central America, and northwestern South America; the differences in plumage are slight and molecular analysis may show that its species status is not warranted.

It is a largely green bird with glimpses of red and black; many of the feathers are margined with contrasting colours giving a finely scalloped effect.

The crown, nape and neck, breast and belly are green while the forehead, lores and cere are red.

It is found in a variety of lowland forest habitats as well as areas containing scattered trees and plantations.

[3] This species has a limited range and is threatened by habitat loss caused by the forests where it lives being cleared for cattle farming and soybean production.